Casting of dentures in metal



April 21, 1925. 1,534,952

H. L. HOBDAY ET AL CASTING 0F DENTURES IN IETAL Filed July 24, 1923 the molten gold rests in a concavity in the Patented Apr. 21, 1925.

' HERBERT LESLIE nonnay AND EnEnEEIcx WM. nunn, 0E iaELBoUnnE, vrc'ronm,

I 1,534,952 PATENT QFFICE.

AUSTRALIA, ASSIGNORS TO NUNNDAY PROPRIETARY LIMITED, OF MELBOURNE, AUSTRALIA, AN AUSTRALIAN COMPANY.

CASTING OE DENTUBES IN METAL.

Application filed J'uly.24, 1923. Serial No. 653,581.

To all whom it may concern:

Be it known that we, HERBERT LESLIE HOBDAY and FREDERICK WILLIAM NUNN, subjects of the King of Great Britain, residing at 90 Collins Street, Melbourne, Victoria, Australia, have invented certain new and useful Improvements in and Connected with the Casting of Dentures in Metal, of which the following is a specification.

-'Our present invention relates to means forcasting plates and other dentures in metal and is principally concerned with the provision of apparatus wherein the retention of the molten metal and the disposal of same is, during the process of casting, rendered more certain.

In the manufacture of dental plates, gold is melted on the investment containing the mould prior to the whole being swung around in a machine to force the metal through sprue holes into the mould. Dlfficulty is often met with in the sprue holes which either let the molten metal pass too freely to the mould or choke the flow, thereby impeding the process. Furthermore, as

investment, there is a liability that some of it may be spilled when theinvestment is swung.

A further known mode of transferring the molten metal to the mould is by placing a wet asbestos sheet over the cavity containing the metal. The heat from the investment generates steam by contact with the wet sheet which steam forces the gold into the mould.

It is to avoid or "minimize this loss of metal and to facilitate the process of manufacturing the plates that our invention has beenprincipally devised, in the effecting of,

which a reducing chamber of specialconstruction is provided for attachment to,- and incorporation with, the investment. The investment is preferably placed in a convenient basket and rotated in a machine to obtain the centrifugal force necessary to convey the molten metal from the reducing cup to the mould. Themachine is of simple construction and is" illustrated, together with the reducing chamber, in the accompanying drawings, in which Figure 1 shows in perspective view an investment and reducing cup, attached thereto, in a basket.

basket is swung.

Figure 2 is a sectional elevation of the reducing cup.

Figure 3 illustrates in side elevation a machine wherein the basket is swung in a vertical plane, and

Figure 4 is a like view of a; machine adapted to swing the basket in a horizontal plane.

The investment 5 is contained within a cylinder 6 held in a basket 7, that is attached to a rigid counterweighted rod' 8 adapted to be rotated with the supporting spindle 9 in the machine depicted in Figure 3. If the basket rod 8 be horizontally placed and rotated, the basket is connected thereto through a link 10 so that the basket, while stationary, will hang vertically therefrom, but will assume a position directly in line with the rod when the latter is swung. We

prefer, however, to use the vertically operating machine of Figure 3 in which the basket is rigidly attached.to the counter: weighted rod 8.

Contained in the investment is the wax mould, and the reducing cup 11 is placed upon the top of the investment and connected to the mouldby a wax sprue that serves to hold it while being invested. On the investment being heated the wax materials disappear leaving the mould free to receive the molten gold from the cup. The

latter is formed. partly closed at the top, but with a suflicient opening to admit the solid metal, such as gold, that is to be reduced to a. molten condition therein. Opposite the'opening the side overhangs inwards at 12 to partially roof in the cup, and the edge is finished with a short depending flange 13. In the floor of. the cup is a single main sprue hole 14 that passes only partly through the floor from below and is immediately in line with the main channel or sprue 16 to the mould. This hole 14 receives the upper .end of the wax sprue from the mould while fixing the cup in position. Communicating with the sprue hole 14 from the floor of the cup are lesser (preferably three or four) small short sprue holes 15 which are not ample enough to permit the molten metal to pass by gravity to the mould but which allow the same. to freely flow,

under pressure\ of centrifugal force, as the In operation, the mould having been invested, the cup 11 is placed in position on the invest-ment and incorporated with the same by additional investing material. l\5[etal is then put in the cup and reduced to a molten condition by heat and the basket is swung in a direction to cause the metal to move up the enclosed side of the cup,

when it will be deflected by the roof 12 and v flange 13 downwards over the sprue holes 15, through which it will be forced under pressure to the main sprue hole 14 and thence to the mould. Thus, the molten metal will be safely retained in the cup during the process and forced into every part of the mould to properly fill the same to form the plate .or denture.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In the manufacture of metal dentures, a mould investment, a reducing cup for the metal arranged on and incorporated with the moulding investment, said cup having partial overhanging roof on one side and a flange depending from the inner edge of said roof, and also having means for conveying the molten metal from the cup to the mould.

2. Inthe manufacture of metal dentures,

a reducing cup, a moulding investment with which the cup- 1s incorporated, said cup having a main sprue in its base that passes only a side and a flange which depends from the inner edge of said roof, said cup also hav-- ing a main sprue in its base that sses only partly through the floor, from low, immediately, over the mould sprue, and small short sprue holes that lead from the upper surface of the cup base to the main sprue, a basket for holding the moulding investment and cup,- a counterweighted rigid rod to which the basket is oonneoted'and means 0 rated with the moulding investment, said cup having a partial overhanging roof on one" for rotating the rod when the cup contains molten metal.

In witness whereof we aflix our signatures.

. HERBERT LESLIE HOBDAY.-

FREDERICK WM, NUNN. 

